Thanks to their simple and sturdy structure, ejectors or jet pumps are often used in so-called regeneration systems of motor vehicles. Regeneration systems bring about a regeneration of the activated charcoal filter which contains fuel vapors. These fuel vapors can be fed to an engine. Such a regeneration system is shown in FIG. 1 by way of an example, specifically for turbocharged engines.
The use of auxiliary components such as, for example, ejectors, in regeneration systems is necessary nowadays since, as a result of consumption-reducing measures in engines, the sources that could generate an adequate negative pressure in the engine over prolonged periods of time are much more limited. Consumption-reducing measures that result in such limitations are downsizing, dethrottling of intake systems, turbocharging, stop-start technologies and, in particular, the hybridization of motor vehicles.
A regeneration that only utilizes an operation-dependent usual negative pressure in an intake manifold or upstream from the compressor of a turbocharger is no longer sufficient. Rather, additional auxiliary components are needed.
In motor vehicles with start-stop technology and in hybrid vehicles, there are times when the internal combustion engine is not running at all, as a result of which no regeneration can even take place at all during these periods of time. However, depending on the climate conditions, fuel vapors continue to be produced.
The above-mentioned technical problems are of particular significance, for example, in the United States where the pertinent legislation requires all motor vehicles to be equipped with a so-called ORVR (onboard refueling vapor recovery) system. The ORVR system has to capture the fuel vapors that escape from the tank during refueling.
These fuel vapors are generally captured with the same activated charcoal filter that also captures the other fuel vapors that escape from the tank. Consequently, in the United States, far greater quantities of purge air are needed to regenerate an activated charcoal filter than, for example, in Europe, where ORVR systems are not required. This is because in Europe, the fuel vapors displaced from the tank during refueling are captured by vapor recovery systems installed on the filling nozzle of the gas station pump. In addition to the above-mentioned requirements, however, there is also a need to reduce permissible emissions even further.
Ejectors are used to assist the regeneration of an activated charcoal filter in motor vehicles having turbocharged engines. Here, an artificial short circuit is created between the compressed air, downstream from the compressor, and the air intake, upstream from the compressor, whereby the pressure gradient is utilized to generate a drive flow. Depending on the charging pressure, an appropriate regeneration flow is then generated to purge the activated charcoal filter.
In the United States, it is also required that the proper functioning of such regeneration systems be regularly monitored during operation by means of so-called on-board diagnostics (OBD) in the motor vehicle.
In a regeneration system according to FIG. 1, the concrete problem arises of diagnosing the line leading from the ejector to the intake system of the turbocharger. This line or the integrity of this line is difficult to diagnose without complicated additional measures or it is even impossible. In FIG. 1, this line is designated by the reference numeral 4a and it is connected to an ejector 4 of the state of the art.
Before this backdrop, the legislation stipulates that monitoring of the outlet side of the ejector is not necessary if it runs inside the walls of the intake system. Here, the overall design has to ensure that an error, for instance, a break, can be diagnosed. Among other things, this led to a configuration as is shown in FIG. 2. In this configuration, the ejector is connected directly to the intake system upstream from the turbocharger. The ejector can be connected to the intake system, among other things, by means of rotowelding.
In the ejector according to FIG. 2, which is directly connected to the intake system, the feed connections are configured in one piece with the ejector. However, this entails the risk that the ejector will be disconnected from the intake system, for example, because of a break, although the fundamental functionality of the ejector will be retained. Then a mixed flow or an outflow on the outlet side would escape from the ejector into the environment, which is not permissible. In particular, this error, however, would not be diagnosable.
An ejector according to FIG. 2 that is connected directly to the intake system is disadvantageous because of its exposed location. The fact that it protrudes quite far relative to a wall of the intake system is detrimental and exposes the ejector to high risks. Impacts and ultimately breaks can occur.